Development of starch based intelligent films by incorporating anthocyanins of butterfly pea flower and TiO2 and their applicability as freshness sensors for prawns during storage

Abstract

Intelligent pH sensitive starch films were developed by incorporation of anthocyanin pigment extracted from butterfly pea flower (BPE) and nanosized TiO₂ using the method of solution casting. This research work evaluated the influence of BPE and TiO₂ on the physical and structural properties of starch films. The physical properties of the starch films could be significantly altered by the addition of BPE and or TiO₂. The starch films S/BPE and S/BPE/TiO₂ exhibited higher barrier properties against water vapour as compared to the control films. Incorporation of BPE and TiO₂ could decrease the thickness and moisture content of films. S, S/BPE starch films were transparent and, S/TiO₂ and S/BPE/TiO₂ films were opaque. Control starch films were colourless, whereas S/BPE films have purple colour. Owing to the inclusion of BPE and TiO₂ particles, structural characterization by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) did not show any major changes in polymer structure. Thermogravimetric analysis revealed that the addition of TiO₂ enhanced the thermal stability of starch films to a significant extent. The color of different starch-based films was determined using the CIE Lab scale under different pH conditions and compared with the control. The fabricated (S/BPE and S/BPE/TiO₂) films exhibited visually perceptible colour changes in the pH range between 1 and 12. Consequently these films could be used as intelligent pH indicators for monitoring the freshness of prawn seafood samples. During the storage of prawn food samples for 6 days, the color of the film changed from light pink to green which is a clear indication of spoilage of food material.